Spraying apparatus



United States Patent O 2,901,178 SPRAYING APPARATUS Edward O. Norris,Westport, Conn. Application August 30, 1956, Serial No. `607,104 1Claim. (Cl. 239-15) This invention relates to a method and apparatus forspray coating articles and has for an object to provide a coating systemhaving novel and improved characteristies.

Another object is to provide improved means to project an ionized sprayinto a spray zone without using exposed high potential electrodes.

A further object is to minimize the possibility of llashover between theatomizer head and the parts being sprayed.

A further object is to provide improved means for producing an ionizedspray using enclosed electrodes, of materials having conductingproperties.

Other objects and advantages will be apparent as the nature of theinvention is more fully disclosed.

The invention will be better understood by referring to the followingdescription, taken in connection with the accompanying drawing whereinspecific embodiments have been set forth for purposes of illustration.

In the drawing:

Fig. 1 is a longitudinal section of a rotary atomizing head embodyingthe invention;

Fig. 2 is a partial transverse section taken on the line 2-2 of Fig. 1;and

Fig. 3 is a detail view of an air jet nozzle embodying the invention.

Referring to'the drawing more in detail the rotary atomizer head isshown in Figs. l and 2 as mounted on the lowerend of an insulating tubewhich provides a bearing and support for the lower end of a drive shaft11 which is driven by a motor, not shown. The shaft 11 and tube 10 areof insulating material. A lower frusto conical atomizer member 12 ofinsulating material is attached to the lower end of the shaft 11 by ascrew 13 and collar 14. An upper frusto conical member 15 is disposedabove the lower head 12 and is held by brackets 16 in spacedrelationship with respect to the lower member 12 to provide a peripheralslot 17 therebetween. A feed pipe 19 extends down along the outside ofthe tube 10 with its lower end terminating in a discharge nozzle 20adjacent the lower inner surface of the member 12 so that liquiddischarged from the nozzle 20 is fed upwardly along the frusto conicalinner surface of the member 12 by centrifugal force and outwardly as anatomized spray through the peripheral slot 17. Bearing 22 for the shaft11 is shielded by a sleeve 23 which is secured to and rotates with themember 12.

An insulating cone 25 is attached to the brackets 16 and divides thehead into an upper compartment 26 and a lower compartment 27. The nozzle20 discharges the liquid for atomization into the lower compartment 27.A set of spring wires 30 are attached to a ring 31 which is mounted tothe tube 10 and is electrically connected to a high tension electriccable 32.

In operation air is drawn in through-passage 33 between the upper member15 and the tube 10 and is forced outwardly through the peripheral slot17 by centrifugal action, contacting the wires 30 and receiving anionizing charge therefrom. This ionized air is mixed with the liquidfrom the lower compartment 27 at the peripheral slot 17 and imparts anionizing charge to the spray. In some cases it has been found advisableto make the non- ICC conducting discs larger in diameter to hold theelectrodes as close to the cable as possible to further isolate theelectrodes.

This apparatus is particularly useful for liquids such as emulsions orsuspensions having conducting or semiconducting characteristics suchthat a charge will feed back through the system. The ionized air impartsa charge to the spray which is formed at the peripheral slot 17 andassists in the atomization. The spray thus formed can be attracted to anoppositely charged or grounded surface such as a metal can shell asshown in my copending application Serial No. 607,105, led August 30,1956, now abandoned.

Fig. 3 illustrates an embodiment wherein feed pipe 40 terminates in anozzle 41 in a mixing chamber 42. Air is supplied from pipe 43 tochamber 44, thence through passages 45 to mixing chamber 42, where it ismixed with the liquid and assists in atomization from jet opening 46.

An electrical charging electrode 48 is disposed in the air pipe 43 andis connected to a high tension electric cable 49.

This embodiment, like that of Figs. l and 2, is useful with liquids ofconducting o r semi-conducting types. The ionized air mixes with theuncharged liquid to impart an ionizing charge to the spray.

The parts which contact the liquid and air streams after ionizationshould be made of non-conducting material such as Bakelite or nylon orthe like in order to minimize loss of charge.

`In some instances it may be desirable to apply an ionizing chargedirectly to the liquid as well as to the air stream, particularly whenthe liquid is nonconducting and is capable of retaining its charge.Various other changes and adaptations will be apparent to a personskilled in the art.

What is claimed:

Apparatus for producing an ionized spray of sprayable material,comprising a rotary spray head including a pair of frusto conicalmembers of electrical insulating material forming a confined areatherebetween and having peripheral edges spaced to provide therebetweena peripheral discharge opening and a radial member of electricalinsulating material disposed between said first members to divide saidconned area into two separate chambers, said radial member havingaperipheral edge spaced from the peripheral edges of said tirst memberto provide a peripheral discharge opening communicating -with each ofsaid chambers, a iluid pipe disposed to feed material for spraying tothe central portion of one ofsaid frusto conical members, means rotatingsaid head to cause said material to flow along the frusto conicalsurface of said last member by centrifugal force and to be dischargedfrom said peripheral discharge opening and a fixed electrode disposedbetween said radial member and the other of said frusto conical members,means connected to pass air through the chamber containing saidelectrodes and outwardly therefrom through said peripheral dischargeopening for mixing with and assisting in the atomization of saidmaterial and electrical connections to apply an ionizing potential tosaid electrode suited tol ionize the air in its passage through saidlast mentioned chamber.

References Cited in the le of this patent UNITED STATES PATENTS1,543,235 Scheminger June 23, 1925 1,854,475 Littlefield Apr. 19, 19322,047,699 MacLachlin July 14, 1936 2,352,252 Carnetta June 27, 1944FOREIGN PATENTS 273,336 Switzerland May 1, 1951 710,852 Great BritainJune 23, 1954

